Maru cat is a YouTube hit.Screengrab from mugumogu on YouTube
Businesses are now spending a whopping $1B per quarter on social media to reach fans through advertising, according to Business Insider's estimates.

And that's not counting resources poured into non-advertising social-media projects like content publishing and sentiment monitoring.

With all this activity, it's crucial to know: what's the best way to measure impact on social media?